The so-called viscose method of producing dissolvable cellulose is generally used in the manufacture of regenerated cellulose. According to this method alkali cellulose is prepared and is reacted with carbon disulfide to form cellulose xanthogenate. The cellulose xanthogenate may be dissolved in alkali solution and regenerated by precipitation in film or fiber form to again become cellulose. However, the carbon disulfide used in this process is an extremely toxic substance and many attempts have been made to find a substitute chemical to replace the carbon disulfide, a chemical which would be sufficiently economical for large scale use and which would not cause the detrimental environmental and health effects of carbon disulfide. However, no commercial method or process has as yet been developed.
Finnish Patent No. 61033 discloses a process for the manufacturing of an alkali-soluble cellulose compound without using carbon disulfide or any other environmentally harmful chemicals. In this method cellulose is heated with urea in an organic liquid in which urea is substantially insoluble. The cellulose carbamate, which is the reaction product, is soluble in alkali and can be precipitated from the solution in fiber or film form. However, although this method results in a degree of solubility of fibers which is sufficient for large scale spinning, the need to use organic solvents in the process causes numerous problems, for example in connection with recovery and purification of waste water.
It is therefore desirable to find an alternative to the use of organic liquids or solvents which can, however, lead to an end result at least as good as that resulting from the process of using the organic solvents.